Cyclopentenolones of formula I: ##STR2##
wherein R.sub.1 is C.sub.1 -C.sub.10 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.10 alkynyl or C.sub.1 -C.sub.4 haloalkyl, are useful as the important alcohol components in a group of ester compounds, commonly called "synthetic pyrethroids," having excellent insecticidal activity.
For example, the compound of formula II below, an ester of 4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2-en-1-one with 2,2,3,3-tetramethylcyclopropanecarboxylic acid, is an excellent insecticide having very strong knockdown activity and mortal activity (see, e.g., JP-B 50-15843/1975). ##STR3##
The cyclopentenolones of formula I include two kinds of optical isomers because they have an asymmetric carbon atom at position 4. In the case of synthetic pyrethroids containing such optical isomers as the alcohol components, it is well known that the difference in optical isomerism between these alcohol components makes a great difference in their insecticidal effects. For example, the compound of formula II above has been found to exhibit several times as excellent insecticidal activity in the case of an ester of (S)-4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2-en-1-one as in the case of an ester of the corresponding (R)-4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2-en-1-one.
For these reasons, there has been a great demand for the development of a method for separating and obtaining the optical isomers of cyclopentenolones of formula I as the intermediates of drugs, agricultural chemicals or other active products in an industrially favorable manner. In addition, for this purpose, in order to prepare a microorganism, for example, by a gene engineering technique, which microorganism can produce an excellent esterase capable of acting upon an organic carboxylic acid ester of a cyclopentenolone of formula I for asymmetric hydrolysis of the ester, the search of a gene coding for such an esterase has also been eagerly desired.